Recent developments in SARS-CoV-2 vaccines: A systematic review of the current studies

Abstract

Designing and manufacturing efficient vaccines against coronavirus disease 2019 (COVID-19) is a major objective. In this systematic review, we aimed to evaluate the most important vaccines under construction worldwide, their efficiencies and clinical results in healthy individuals and in those with specific underlying diseases. We conducted a comprehensive search in PubMed, Scopus, EMBASE, and Web of Sciences by 1 December 2021 to identify published research studies. The inclusion criteria were publications that evaluated the immune responses and safety of COVID-19 vaccines in healthy individuals and in those with pre-existing diseases. We also searched the VAERS database to estimate the incidence of adverse events of special interest (AESI) post COVID-19 vaccination. Almost all investigated vaccines were well tolerated and developed good levels of both humoural and cellular responses. A protective and efficient humoural immune response develops after the second or third dose of vaccine and a longer interval (about 28 days) between the first and second injections of vaccine could induce higher antibody responses. The vaccines were less immunogenic in immunocompromised patients, particularly those with haematological malignancies. In addition, we found that venous and arterial thrombotic events, Bell's palsy, and myocarditis/pericarditis were the most common AESI. The results showed the potency of the SARS-CoV-2 vaccines to protect subjects against disease. The provision of further effective and safe vaccines is necessary in order to reach a high coverage of immunisation programs across the globe and to provide protection against infection itself.

Keywords: COVID-19; SARS-CoV-2; efficacy; immune system; immunogenicity; vaccine.

FIGURE 1

SARS‐CoV‐2 major structural proteins and summary of strategy types for COVID‐19 vaccine designing

FIGURE 2

Flow diagram of study selection

FIGURE 3

Vaccine‐induced immune responses. Antigen‐presenting cells (APCs) including dendritic cells (DC) can process and present vaccine antigens to both CD4+ and CD8+ T cells. CD4+ T cells that activated by SARS‐CoV‐2 vaccine antigens presented by APCs can production Th2 cytokines which help B cells to differentiate into plasma cells and memory B cells. The activated B cells can produce neutralising antibodies (nAbs). CD8+ T cells can be activated by Th1 cytokines and acquire the ability to attack and lysis the SARS‐CoV‐2 infected cells